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First-Principles Computations for KTN

S. Prosandeev·E. Cockayne·B. Burton·A. Turik
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Abstract

Solid solutions of KTaO$_{3}$ and KNbO$_{3}$ (KTN) exhibit unusual dielectric properties at ferroelectric phase transitions, which are usually associated with a Nb instability that is often explained by the large Nb dynamical charge in oxides. Using non-self-consistent VASP computations, we showed earlier that the Nb dynamical charge in layerd KTN strongly depends on the local environment of Nb. In the present study, we have performed self-consistent first-principles computations for fixed composition KTa7/8Nb1/8O3 in different configurations shown. We computed the equilibrium ionic positions, Born charges, force constants, vibration frequencies and modes. We also discuss the question whether Nb has a multi-well potential, and the field dependence of susceptibility.

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S. Prosandeev, E. Cockayne, B. Burton, A. Turik. 2004-01-07. First-Principles Computations for KTN. https://arxiv.org/abs/cond-mat/0401039

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